Foliar respiration is related to photosynthetic, growth and carbohydrate response to experimental drought and elevated temperature

Short-term plant respiration (R) increases exponentially with rising temperature, but drought could reduce respiration by reducing growth and metabolism. Acclimation may alter these responses. We examined if species with different drought responses would differ in foliar R response to +4.8 degrees C temperature and -45% precipitation in a field experiment with mature pinon and juniper trees, and if any differences between species were related to differences in photosynthesis rates, shoot growth and nonstructural carbohydrates (NSCs). Short-term foliar R had a Q(10) of 1.6 for pinon and 2.6 for juniper. Pinon foliar R did not respond to the +4.8 degrees C temperatures, but R increased 1.4x for juniper. Across treatments, pinon foliage had higher growth, lower NSC content, 29% lower photosynthesis rates, and 44% lower R than juniper. Removing 45% precipitation had little impact on R for either species. Species differences in the response of R under elevated temperature were related to substrate availability and stomatal response to leaf water potential. Despite not acclimating to the higher temperature and having higher R than pinon, greater substrate availability in juniper suggests it could supply respiratory demand for much longer than pinon. Species responses will be critical in ecosystem response to a warmer climate.